In printing systems, and especially in roll-to-roll printing systems, in which printed sheet output from the system is gathered by winding the sheet onto a take-up roll, there is always the issue of managing the work-flow from the printing system when the take-up roll is full, i.e. when it reaches its maximum sheet-carrying capacity. At that time, it becomes necessary to replace the full take-up roll at the output end of the printing system, which typically requires a manual intervention by a system operator. The same applies if the take-up roll is to be changed because the current print job has just finished. If the printing continues during the change-over of the take-up roll, the printed sheet may be collected in a buffer zone until the new take-up roll is installed and is ready for taking up (e.g. winding up) the printed sheet. The time required for a manual intervention by an operator to change-over the take-up roll in this regard is typically several minutes. If an excessive amount of time is required by the operator, the printed sheet accumulating in the buffer zone can become creased or damaged. In an extreme case, the printing system must be temporarily interrupted, which has a significant negative impact upon system productivity, as well as on the print quality of the printed sheet after re-starting the printing. It is therefore desirable to improve the speed and efficiency of changing-over take-up rolls in a printing system.
DE2912656 A1 describes a mechanism which feeds endless paper or individual sheets as desired into a typing mechanism, having a roller transporting the inserted paper into the typing position, and feed, guide and transport devices for paper and sheets separately, directing them into a common shaft.
US2013100223 A1 describes a sheet conveyance apparatus comprising a loop forming unit that is disposed on a sheet conveyance path and bends, in a loop, the sheet to be conveyed, and a guide unit that is stepwise high at both sides whereas low at the center, as viewed in a sheet conveyance direction, and extends in the sheet conveyance direction, wherein the sheet sagging in the loop by the loop forming unit enters a guide region being defined between opposite guide faces of paired steps in the stepwise guide unit and having a width according to the width of the sheet, so that the side edges of the sheet abut against the guide faces, thus correcting the skewing of the sheet in the sheet conveyance direction.